Two key healthcare aspects for individuals impacted by opioid use disorder are readily available treatment services and in the event of an overdose, emergency medical services. This research involved an analysis of spatial access to both of these key service types in New Hampshire, a state that has been highly impacted by unintentional heroin and fentanyl deaths, and the subject of a National Drug Early Warning System (NDEWS) HotSpot Study on unintentional overdoses involving fentanyl. We discuss our approach for designing a composite index of spatial access that used the enhanced two-step floating catchment area (E2SFCA) model integrated with Huff model for modeling spatial access to treatment centers and buprenorphine physicians, as well as a modified version of the E2SFCA to evaluate access to emergency medical services. The models account for treatment service availability, estimated demand for services, and driving times and distances across the State. The results revealed locations where an imbalance of access to substance use disorder treatment services was estimated. The spatial patterns of access were computed for two different time periods and compared to determine how access to these key treatment services has evolved in New Hampshire. The insights from this research provides guidance for local public health officials who are tasked with planning strategies for substance use treatment services especially in high-risk regions.